Recently, an image forming apparatus such as an MFP (Multi Function Peripheral) has been commercially available such that a display screen equipped with a touch panel as a user interface (hereinafter, also referred to as UI) is made larger with various functions such as a preview function which are easier to be used and improved so as to be easily viewable. With the trend toward high functionality or multifunctionality for the MFP in this manner, a load on a CPU provided in the MFP of course increases.
When processing ability of the CPU becomes insufficient, operation of the MFP is suppressed so that a user gets stressed because, for example, preview display is not smoothly performed, scan performance is degraded, or the like. In this case, a high-performance CPU with high processing ability is attached to the MFP so as to be able to attempt load reduction, however, the high-performance CPU is generally expensive, thus causing cost increases of the MFP. Therefore, various techniques have been proposed to use the CPU effectively without stressing a user out.
For example, Japanese Laid-Open Patent Publication No. 2007-164481 describes an MFP capable of dynamically changing job priority or a maximum executable number of jobs by an operating rate of a CPU or the like. With this MFP, a print job, a fax transmission job, an application execution job, and a mail transmission job are spooled in a spool queue, in which a job control portion calculates the number of jobs simultaneously executable based on job priority, and allows execution of the job having high priority even when the number of the executable jobs reaches a limit, then executes a job by a corresponding job execution task. The priority is corrected by the operating rate of the CPU to allow efficient execution of the job.
Here, in the case of processing a job with a high CPU load in the MFP, CPU utilization becomes nearly 100% in some cases. In this case, the CPU is occupied by job processing, thus influencing operation of a UI in the MFP. For example, responsiveness of the UI is degraded so that preview display is stopped on the way, operation of screen switching and the like become awkward, or the like, thus heavily stressing a user out with such a state which is directly visible.
Since it needs to put some flexibility into CPU utilization in order to smoothly operate the UI of the MFP, it is expected that the CPU utilization for being allocated to job processing or other functions is suppressed to, for example, about 80 to 90%. However, a high load is applied to the CPU depending on a job in some cases, thus posing a problem that it is difficult to suppress the CPU utilization up to 80 to 90% all the time. Moreover, to the contrary, placing priority on the operation of the UI influences processing of a job with a high load, thereby, for example, temporarily stopping print processing by a printer or reading processing by a scanner, or the like, thus stressing the user out also in this case.
For addressing such a problem, the technique described in Japanese Laid-Open Patent Publication No. 2007-164481 is to dynamically change job priority depending on CPU utilization, and not to attempt smooth operation of a UI without temporarily stopping processing of various jobs, thus not to solve the problem as described above.